1. Field of Invention
The present invention relates to an apparatus and a method for rubbing liquid crystal display (LCD) substrates. More particularly, the present invention relates to an apparatus and a method for rubbing the alignment layer in the LCD substrate.
2. Description of Related Art
The cathode ray tube (CRT) has dominated our desktops and living rooms for half a century as the standard display for monitors. However, the CRT is now facing real competition in the form of monitors or display panels based on liquid crystal displays (LCDs).
Most of the LCD devices using electro-optical effects of liquid crystals as a light modulator, such as the twisted nematic (TN)-effect and the in-plane switching (IPS)-effect for thin film transistor liquid crystal displays (TFT LCDs). The most common LCD in use today is TFT-LCD, having a sandwich-like structure with liquid crystal filled between two glass plates.
The liquid crystal is the material that possesses properties of the liquid including fluidity and the solid including long-range order at the same time. Liquid crystal molecules have unique structures in a bar shape, and they have the anisotropic characteristics.
Liquid crystal displays in use rely on pixels formed by liquid-crystal (LC) cells that change the polarization direction of light passing through them in response to an electrical voltage. The polarization orientation of the liquid crystal molecule is determined by the rubbing direction of the alignment layer.
Rubbing process is commonly used by most LCD manufacturers to forms the straight groove in a fixed direction on the hardened alignment layer, so that the liquid crystal molecules can align in the fixed direction. The rubbing process is performed through mechanical contact between the rubbing roller and the alignment layer. However, if the rubbing roller degrades unexpectedly or unevenly, the effect of a local defect on the alignment layer may not be detected until hundreds of flawed displays have been manufactured and subsequently discarded. Moreover, rubbing rate is deferred to a large extent by the poor conditions or instabilities of the rubbing roller. Therefore, it is in great demand to improve the rubbing roller or the present rubbing process, in order to increase reliability and enhance rubbing performance.